Floor grinder



A. W. MALL FLOOR GRINDER Nov. 3, 1942.

Filed May 13, 1940 4 Sheets-Sheet 1 ATTORNEY.

1942- A. w. MALL 2,301,164

FLOOR GRINDER Filed May 13, 1940 4 Sheets-Sheet 2 away/Mm WW BY W Xaa;

ATTORNEY.

3, 1942- A. w. MALL 2,30l,l64

FLOOR GRINDER Filed May 13, 1940 v I 4 Sheets-Sheet 5 IIIlIlIIII llllllIIIIITII I as 8! yams I am; WMWZZ? BY flea/4 fuzz,

ATTORNEY L Nov. 3, 1942. A. w. MALL 2,301;1.64

FLOOR GRINDER Filed May 13, 1940 4 Sheets-Sheet 4 INVENTOR.

am mm mm Wghm ATTORNEY.

Patented Nov. 3, 1942 UNI TED STATES PAT EN T O FF! CE FLOOR-GRINDERArthur William Mall, Flossmoor, Ill. Application'May 13, 1940, SerialNo. 334,791

2 Claims. 01. 51 -177) My invention relates in general 'to an improvedfloor grinding machine of the type specially adapted for high speedgrinding of'hard surfaces, such as terrazzo floors.

The inventionrelates more particularly to the type of floor grinder inwhich the weight of the grinding wheel and its associated parts providesthenecessaryinertia Weight for maintaining the desired downward pressureon the grinding wheel during the grinding operation.

"In thefi'oor grinding machines whichare'commercially available todaythe grinding wheels are run at "low speeds, seldom exceeding 800 RP. M.In "the grindingof floorsh'aving teriazzo surfacing it is necessary togrind away only, are availablecommerciallytoday is thefact that whengrin'ding' at'higher speeds, it is more diflicult to obtain a smoothlyground surface. With high speed grinding it is difiicult to avoid theformation of small ridges inthe surface being ground.

My invention primarily contemplates a .com

bination of-elements'which unite to form a ,high speed grinding machinecapable of grinding a greatly increased amount of floor space per unitof time and also capable of grinding the surface 3.;

to a smooth finish. I

Gne of the problems encountered in the construction of a machine of thistype is to control the amount of inertia weight supported by thegrinding wheel to compensate for the difierent types of surfaces to beground and for the different types of motors that may be used to run themachine.

Another problem is'to-provide a;flexible supporting means for thegrinding wheel and in 3;:

connection therewith to provide a drive shaft between the motor and thegrinding wheel, which will permit the desired flexibility and which willabsorb any shocks and jars resulting from irregularities in the surfaceof the floorand at'the same time assure a constantly smooth runninggrinding wheel. In my prior floor grinding machines 'I have .found thatthe use of a flexible shaft for driving the grinding wheel (such as is.:shown in my Patents Nos.

2,097,730 and 1,989,491) is not wholly satisfactory. Due to thetremendous torque transmitted through the shaft, its normal life isshortened. l'have also found that it is not satisfactory to use a rigiddrive shaft because such a shaft makes it impossible to flexibly'supportthe grinding head assembly.

By using a single flexible coupling between the motor and grindingwheel, I have made it possible to flexibly support the grinding headassembly, to provide a constantly smooth running grinding wheel, and toshorten the over-{all length of the machine;

Still another problem is to maintain thel'fa'ce of the grinding wheellevel with the surface'being ground so as to prevent any ridges beingleft in'the surface.

Theinvention contemplates a solution'to all of these problems.

One object ofthe invention is to provide means for controlling "theamount of inertia weight resting on the grinding Wheel. 7

Another object is to provide a more compact machine which is lessexpensive to manufacture,

more efficient, and easier to operate. 7 w

A further object is to so arrange the Parts "of the machine that'itsweight is distributed more evenlythroughout the entire device.

A further object is to provide means for effecting fine adjustment ofthe level of" the grindingwheel with relation to the floor surfaceand'for varying the ultimate flexibility of the grinding head assembly.

sand hopper into thespindle housing.

Another object is to provide improved means a for supporting thegrinding wheel so that it is universally flexible and tiltable.

Other objects and advantages willbe more apparent from the followingdescription, wherein reference is had to the accompanyingdrawingsinwhioh: a

.Fig. -1 is a side elevation of my improved machine with the grindingheadbroken in-section and showing the adjustable Wheel supports in anadvanced position;

Fig. 2 is an enlarged View of the gate for controlling the flow of sandfrom the sand hop- Eig. 3 is a. rear end view .of the machine showing insection the hand wheel adjusting means for raising and lowering themotor;

Fig. 4 is a side view of one of the adjustable wheel support arms;

Fig. 5 is a fragmentary view of the spindle housing and grinding headpartly in section;

Fig. 6 is a plan view of the spindle housing partly in section;

Fig. 7 is a modification of my invention; and

Fig. 8 is a front view of the spindle housing shown in Fig. 7.

Referring to Fig. 1 my invention comprises generally a horizontallydisposed motor M, a wheeled carriage for the motor, a spindle hous ing Swith a cup-face grinding wheel G at the lower end thereof. The means fordriving the grinding wheel may comprise generally the construction shownin my Patent No. 2,097,730 including bevel gears secured to a hollowspindle shaft and drive shaft, the shafts being journalled in suitableball bearings. A conventional double acting universal joint U isinterposed between the motor and spindle housing providing a flexibledrive shaft, the reason for which will appear later. A tube extendsthrough the hollow spindle shaft for conducting sand and water to thegrinding wheel.

The motor M may be of a special type of heavy duty motor capable ofoperating at a free speed of 3600 R. P. M. and its capacity may be 5 H.P. or 10 H. P. depending upon the types of current available. The motoris carried by support wheels in which may be provided with rubber tires20 for assuring a firm grip upon the floor during the operation of themachine and for preventing the possibility of marring and scratching thesurface being ground. The support wheels Ill are rotatably journalledon. stub shafts extending from hubs The hubs may be formedintegrallywith the support arms l2 which are secured to frame member l3by means of bolts l4. There may be a plurality of openings IS in theframe member for receiving the bolts l4 so that the support arms |2 maybe adjusted forwardly or rearwardly with respect to the motor.

When the support arms are adjusted to a forward position (as shown inFig. 1) the motor acts as a counterbalancing weight, thereby reducingthe total inertia weight supported by the grinding wheel and when thesupport arms are adjusted to a rearward position (as shown in dottedlines in Fig. l) the total inertia weight supported by the grindingwheel is obviously increased. The importance of providing a means forcontrolling the inertia weight supported by the grinding wheel istwo-fold. It makes it possible to adapt the machine to the grinding ofsurfaces which vary in substance and in hardness, such as wood,concrete, stone, or tile surfacesit being obvious that more inertiaweight upon the grinding wheel would be desired when grinding a hardsurface than when grinding a softer surface. Secondly, when it isdesired to change from a 5 H. P. to a 10 H. P. motor, it is necessary toincrease the inertia weight carried by the grinding wheel because of theincreased power being transmitted to the grinding wheel.

hopper H, a water pipe 49 for conveying water to the spindle housing, asupport member 56, and a pair of handle support brackets 68. A handwheel2| may be rotatably mounted upon the housing I! directly above the motorand may be keyed to a screw 22 which is threaded into a sleeve 23. Thesleeve is slidably journalled within the housing spline 24 preventingthe sleeve from rotating when the handwheel and screw is rotated.Secured to the motor M is a bracket 25 having feet 25 formed integrallytherewith. The motor is removably secured to a mounting plate 28 bymeans of bolts 29. The mounting plate may have a centrally locatedopening for receiving the sleeve 23. Thus it may be seen that byrotating the handwheel, the screw member 22 causes the non-rotativesleeve 23 to slide up and down within the housing I1, thereby raisingand lowering the motor which is supported by the sleeve. With thegrinding wheel operating at such high speeds as 3450 R. P. M., it isessential that the working face of the wheel be maintained level withthe surface of the floor. To accomplish this it is necessary to raise orlower the motor so that its longitudinal axis is in parallel alignmentwith the surface of the floor. When the motor is in this position, thegrinding wheel operates best. The handwheel 2| and its associated partsperform this function. In addition, the motor may be lowered tocompensate for grinding wheel wear.

To those who are skilled in the construction of concrete floors withterrazzo surfacing, it is known that slight waves and irregularitiesalways appear on the surface after it has been trowelled and allowed tosetthe surface is never level. I have found that it is largely due tothis circumstance, that the grinding head must be flexibly supported aswell as maintained level with the surface of the floor. The flexibilityassures that the grinding wheel will con- .form to the contour of thesurface being ground.

The importance of these features of flexibility and of maintaining theface of the grinding wheel at a true level with the surface being groundis emphasized as the speed at which the grinding wheel revolves isincreased.

To obtain flexibility of the grinding head I have provided resilientleaf spring supports 39 extending from brackets 3| which are secured tothe forward end of the motor. The outer ends of the leaf springs arereceived in longitudinal slots of brackets 32 which are mounted one oneach side of the spindle housing S. The brackets 32 may be provided withhub portions 34 which slidably and loosely fit over studs 35 (best shownin Fig. 1) which extend outwardly from and are formed integrally withthe spindle housing S. There may be a 1 6" clearance, designated at 35,between the inner wall of the hub portion 36 and the periphery of thestud 36, the reason for which will later appear. After the brackets arefitted onto studs 35, they are supported in position by means of anintermediate bracket 3'! secured between and maintaining brackets 32 ina fixed spaced relation relative to each other.

Although the flexibility of the grinding head together with the meansfor raising and lowering the motor provide a means for adjusting thelevel of the face of the grinding wheel relative to the surface, yetthis does not assure the precision adjustment necessary for high speedgrinding. I have found that even after adjusting the motor up or down sothat the face of the grinding wheel is flat upon the surface to beground, yet when the grinding wheel is revolving at the high speed of3450 R. .P. M., it usually has-a tendency to grab on one side of thewheel, thus causing the entire machine to follow in the direction of thegrab. To eliminate this undersirable feature, I have provided means foreffecting accurate adjustment of the level of the grinding wheel.

A shoulder or flange38, preferably formed integrally with the spindlehousing S, may extend outwardly therefrom into a recess 39 of bracket31. The bracket 3! may be provided with centrally located bores -4:) onits upper and "lower sides into which set screws ll and 42 are threaded.Compression springs and 44 are interposed between the set screws and theflange 33 and may be retained in position by any suitable means, such.as providing corresponding annular shoulders (not shown) on the setscrews and on the flange 38.

Thus it can be seen that by tightening set screw 4! and loosening setscrew 42, the tension on spring 43 is increased and the tension onspring 44 is decreased. Thus the shoulder 38 is urged downwardly anda-longtherewith, the spindle housing and grinding wheel. adjusting ofthe set screws 4| and 42 only slightly affects the levelling of thegrinding wheel, yetit is this circumstance which assures accurateadjustment of the level of the wheel. This parfects the levelling of thegrinding wheel in its front and rear regions.

I have also provideda similar adjusting means on either side of thespindle housing for levelling the grinding wheel from the sides.described, 'the brackets 32 areprovided with hub portions which looselyreceive studs 36 extending outwardly from the spindle housing. l he hubportions 34 are recessed in their upper regions to receive a tensionshoe 45 (best shown in Fig. l) which is interposed between stud 36 andset screw 41. The set screw is threaded into the retainer 45 whichextends upwardly from and is preferably formed integrally with bracket32. Corresponding adjusting meansare provided on the opposite side ofthe spindle housing and are designated generally by correspondingnumerals 45a, 45a, 47a and 48a. Thus 'it is apparent that when set screwis tightened, the increased tension on compression spring 46 causes theshoe 45 to urge the stud 35 downwardly and along therewith the spindlehousing and grinding wheel. A similar action takes place when set screw41a is tightened. The clearance .35 between .the periphery of the studand the inner wall of the hub portion .34 allows a slight upland downmovement of the spindle housing relative to its supporting brackets 32.

It is sometimes desirable to increase or decrease the flexibility of thegrinding head assembly depending upon the type and condition of thesurface being ground. I have provided for th s by incorporating into thewheel levelling adjustment means compression springs for varying heflexibility of the grinding head assembly. It should be apparent that bytightening the set screws 4|, 42, 4'. and 4111 the resulting increase oftension on the compression springs 43, 44, 46 and 45a limits themovement of the spindle housing relative to its supporting brackets 32and 31 and as a consequence thereto limits the ultimate flexibility ofthe entire grinding head assembly, including the aforementionedbrackets. Thus by tightening or loosening the set screws, theflexibility of the grinding head may be varied.

Although the x As previously t adjusted level of the grinding wheel.

the spindle housing.

It is of special significance that the'fiexibility of-the grinding headmay be varied 'by'tightening or loosening the set screws withoutaffecting the For example if it is desired to increase the flexibilityof the grinding head, all of the set screws may be loosened. Byloosening each set screw the same number of turns it is apparent thatthe tension on eachof the compression springs is correspondingly reducedand the adjusted level of the grinding wheel remains constant.

Secured to the rear and upper end of the sand hopper is thewater'conduit il formed integrally with the support member Ell. Upon thesupport number 5 ismounted an elongated casing through which the powercable extends.

An iron water pipe 52 is also mounted on the support ;member 5%} andextends upwardly to substantially the same heighth as the casing 5|.Thus it can be seen that the water line and cable are supported wellabove the machine so as not to interfere with the moving of the machineabout the surface being ground. At the upper end of the water pipe awater hose (not shown) is connected and leads to a remote overhead watersupply (not shown). A suitable valve 53 controls the amount of waterallowed to flow into the receptacle 54.

At the mouth of the sand hopper H is a gate comprising a handle 56 and adisoshaped base portion 5-! closing the mouth of the hopper. Anadjustment screw 53 operating against the handie 55 accurately controlsthe amount of sand that is allowed to flow into the receptacle 54. It isof significance that the sand hopper can be easily cleaned out in caseof clogging by opening the gate 55 and forcing a stick into the mouth ofthe hopper. A power cable 59 extends along the side of the hopper to theswitch box 6!] which is secured to the front hopper wall and thence tothe motor M.

The grind ng wheel G may be secured to the spindle shaft by any suitablesecuring means. Covering the grinding wheel is a guard assembly whichcomprises a mounting plate El secured to A steel band E32 is welded orotherwise secured to several strap members 63 having inwardly turnedflanges which rest loosely upon the mounting plate Bl.

Thus it can be seen that the guard. automatically moves upwardly as thegrinding wheel wears off. A band of rubber Ed is placed about the guard62 and extends slightly beyond the lower edge thereof. As the i uachineis moved over the surface being ground, the rubber band scrapes it cleanand the operator can see the work as it progresses, withp out having tostop the machine and manually clean the floor. The band may be moveddown wardly as its bottom edge wears off. A removable rubber ring 65 isplaced about the rubber band so that when the machine is grinding alonga wall, the rubber ring prevents any possible scratching or marring ofthe wall. When the machine is grinding along a wall which is providedwith a cove base, the rubber ring acts as a gauging device preventingthe grinding wheel from coming into contact with the coving.

A telescopic U-shaped handle 65 may be provided for manipulating themachine about the surface. The lower ends of the handle are slidablyreceived by the elongated sleeve members 5'! which in turn are receivedby the handle support brackets 53. The handle support brackets arepreferably formed integrally with the frame member I 3, there being oneon each side of the housing ll, The handle 66 may be adjusted up or downwithin the sleeves 61 and the clamp 6B retains the handle in itsselected adjusted position. The handle may be withdrawn from the sleevesand reversed as shown in the dotted lines in. Fig. l permittingoperation of the machine close to the walls, A resilient bumper guard 70extends beyond the rear end of the motor for protecting the walls fromscratches, etc.

In Figs. '7 and 8, I have shown a modification of my invention wherein Iprovide a combined water tank W and sand hopper H with a partition Wallseparating them. The flow of sand from the sand hopper is regulated bythe gate member 14 and the flow of water from the water tank isregulated by valve 13. A U-shaped handle i is slidably received inbrackets 16 mounted on each side of the switch box [8. Screw l1 retainsthe handle in any selected position of up and down adjustment. A rubberbumper member 86 is provided at the rear end of the motor housing andserves the same purpose as the spring bumper shown in Fig. 1.

The grinding head assembly is flexibly supported by means of twistedspring members 80 which consist of two strips of flat spring steeltwisted so that the middle portions 89 are horizontal relative to thefloor surface and the end portions 91'! are vertical. Thus it can beseen that the springs are flexible both laterally and vertically. Theend portions of the springs are secured to the spindle housing and tothe front of the motor housing. At the spindle housing the ends of thesprings are secured to a rubber bushing 8! by means of a bolt 82threaded into a nut 83. The nut 83 is bonded to the rubber bushing 8!,The rubber bushing is secured to the wall of the spindle housing bymeans of a bracket 85 which is also bonded to the rubber bushing. Thusit can be seen that the spindle housing is flexibly supported by meansof the spring members 80 through the medium of rubber cushions.

I have found that the combination of a flexible coupling together withthe rubber mountings for the spindle housing are primarily instrumentalin the provision of a high speed machine which will successfully grind asmooth surface on terrazzo floors at a greatly increased rate of speed.

In the spindle housing, as shown in Fig. 8, the sand and water tube 93is journaled centrally therethrough. At the lower end of the tube I haveprovided a spacer bushing 94 between the hollow spindle shaft 95 and thetube and a flange 96 which prevents dust and dirt from searching intothe spindle housing.

Having thus described my invention what I claim is:

1. A surface grinding device comprising a mo tor, a grinding wheeldriven thereby, said grinding wheel adapted to rest of its own weight onthe surface to be ground, a casting positioned directly above the motor,said casting having a base portion, a pair of side walls integral withthe base portion and extending downwardly therefrom so as to partiallyembrace said motor, a tubular housing portion integral with the baseportion and extending substantially vertically upwardlyfrom the baseportion, said housing portion being centrally located on said baseportion, an arm integral with the base portion and integral with a wallof the housing portion, said arm extending angularly outwardly andupwardly from the base and housing portions, wheeled supporting legssecured to the side walls of said casting and embracing the motor, meansfor supporting the motor relative to the wheeled supporting legs saidmeans also serving for adjusting the motor up and down relative to thefloor surface, said means including a hand wheel supported by thehousing portion and a threaded rod extending through the interior of thehousing portion and having connection with the motor, and a fluidcontainer tank supported by the free end of the arm in a plane above theupper level of the motor, said tank being located intermediate the motorand the surfacing wheel,

2. A surface grinding apparatus comprising a motor, a grinding wheeldriven thereby, said grinding wheel adapted to rest of its own weight onthe surface to be ground, a casting positioned directly above the motor,said casting having a base portion, a pair of side walls integral withthe base portion and extending downwardly therefrom so as to partiallyembrace said motor, a tubular housing portion integral with the baseportion and extending substantially vertically upwardly from the baseportion, said housing portion being centrally located on said baseportion, an arm integral with the base portion and integral with a wallof the housing portion, said arm extending angularly outwardly andupwardly from the base and housing portions, wheeled supported legssecured to the side walls of said casting and embracing the motor, meansfor supporting the motor relative to the wheeled supporting legs saidmeans also serving for adjusting the motor up and down relative to thefloor surface, said means including a hand wheel supported by thehousing portion and a threaded rod extending through the interior of thehousing portion and having connection with the motor, and a fluidcontainer tank supported by the free end of the arm in a plane above theupper level of the motor.

ARTHUR WILLIAM MALL.

